1. Field of the Invention
The present invention relates to a vehicle brushless AC generator with cooling function by cooling liquid.
2. Description of the Prior Art
FIG. 5 is a sectional view of a vehicle brushless AC generator disclosed in Japanese Published Patent Application No. Hei 4-68850. In FIG. 5, reference numeral 50 denotes a generator case consisting of a bowl-shaped front bracket 51, a bowl-shaped rear bracket 52 and a cylindrical housing 53 which are joined to separate an inner parts housing chamber 54 from an outer first cooling chamber 55. Reference numeral 56 denotes an o-ring-like sealing member disposed at a joint portion between the front bracket 51 and the rear bracket 52. Numeral 57 is a gasket disposed at a fitting portion between the front bracket 51 and the housing 53. Numeral 58 is a gasket disposed at a fitting portion between the rear bracket 52 and the housing 53. Numeral 59 is an inlet portion provided on the rear bracket 52. Numeral 60 is a cylindrical stator consisting of a stator magnetic pole 61 and a stator coil 62, secured to the housing 53. Numeral 63 is a generator shaft rotatably mounted on the center portions of the front bracket 51 and the rear bracket 52 through a front bearing 64 and a rear bearing 65. Denoted by 66 is a pulley secured to the generator shaft 63 projecting forward from the front bracket 51, adapted to rotate with the shaft 63. Numeral 67 is a rotating magnetic pole. It is provided with a first rotating magnetic pole 68 secured to the generator shaft 63 to rotate therewith in the parts housing chamber 54 and a second rotating magnetic pole 70 secured to a peripheral portion of the first magnetic pole 68 through a supporting ring 69. Numeral 71 is an exciter consisting of an exciting magnetic pole 72 secured to the rear bracket 52 and an exciting coil 73 mounted on the exciting magnetic pole 72. It is housed in a cylindrical housing portion 74 formed in the rotating magnetic pole 67. An air gap is respectively formed between the stator 60, the rotating magnetic pole 67 and the exciter 71. Numeral 75 is a heat conductor provided to radiate the heat from the exciter 71 and disposed to pass through the rear bracket 52. Numeral 76 is a sealant disposed at a portion where the heat conductor 75 passes through the rear bracket 52. Numeral 77 is a plate-shaped cooling cover secured to the rear bracket 52 to form a second cooling chamber 78 between itself and the back face of the rear bracket 52. Numeral 79 is a communication passage formed on the rear bracket 52 to allow the first cooling chamber 55 to communicate with the second cooling chamber 78. Numeral 80 is a gasket disposed at a fitting portion between the rear bracket 52 and the cooling cover 77. Numeral 81 denotes a voltage regulator secured to the back face of the cooling cover 77; numeral 82 a voltage regulator terminal; numeral 83 a rectifier secured to the back face of the cooling cover 77; numeral 84 a rectifier terminal; numeral 85 a stator terminal projecting outward from the housing 53 to be connected to the rectifier terminal 84; numeral 86 an outer terminal provided near the rectifier 83; and numeral 87 a connector for the outer terminal 86, connecting to the voltage regulator terminal 82. Numeral 88 is a protective cover secured to the rear bracket 52 to cover the cooling cover 77, the voltage regulator 81, the voltage regulator terminal 82, the rectifier 83, the rectifier terminal 84, the stator terminal 85, and the connector 87, respectively. Numeral 89 is an opening formed on the protective cover 88 to allow the outer terminal 86 to project from the protective cover 88. Numeral 90 denotes a cooling fluid.
A description is subsequently given of the generating operation of the conventional vehicle AC generator when it is mounted on an automobile. The vehicle brushless AC generator is first installed outside a cylinder block of an engine, then a ring-shaped belt is stretched between a pulley provided on a crankshaft of the engine and the pulley 66 of the AC generator, and electric wiring is installed between the outer terminal 86 and a battery of the automobile. In such a condition, when a driver turns on an ignition switch of the automobile, a current runs from the battery of the automobile to an ignition coil to start the engine. At the same time, an exciting current runs through the voltage regulator 81 from the battery to the exciting coil 73 to make a magnetic circuit between the stator magnetic pole 61, the rotating magnetic pole 67 and the exciting magnetic pole 72. When the generator shaft 63 is turned by starting the engine to rotate the rotating magnetic pole 67, the first rotating magnetic pole 68 and the second rotating magnetic pole 70 cross the stator magnetic pole 61 alternately to allow alternating magnetic flux to pass through the stator coil 62, thereby generating 3-phase AC induced electromotive force in the stator coil 62. The voltage of this induced electromotive force (EMS) is first regulated by the voltage regulator 81 and this EMS is then rectified by the rectifier 83 and charged into the battery through wiring (not shown here) from the outer terminal 86.
Next, the cooling operation of the conventional AC generator mounted on the automobile is explained. The vehicle brushless AC generator is mounted on the engine, and the inlet portion 59 and an outlet portion (not shown) are connected through wiring (not shown) to an engine cooling system. After the AC generator starts the generating operation after the engine is started, a water pump of the engine cooling system is driven to circulate the cooling fluid when the temperature of the engine rises over a predetermined temperature. In such a condition, the cooling fluid 90 shown by a dotted line moves as shown by an arrow X through the inlet portion 59 to the first cooling chamber 55 and through the communication passage 79 to the second cooling chamber 78 in sequence. In the first cooling chamber 55 and the second cooling chamber 78, the heat generated from parts such as the stator 60, the exciter 71, the voltage regulator 81 and the rectifier 83 by the generating operation is absorbed by the cooling fluid 90 as a result of heat exchange action with the cooling fluid 90. The cooling fluid 90 that has absorbed the heat is then returned through the outlet portion to the engine cooling system. (A structure similar to this cooling system is disclosed in FIG. 12 of Laid-Open Japanese Patent Application No. Hei 8-130854).
However, in the conventional AC generator stated above, the first cooling chamber 55 is formed in a manner completely separated from the parts housing chamber 54 by the three independent parts of the front bracket 51, the rear bracket 52 and the cylindrical housing 53. On the other hand, the second cooling chamber 78 is also formed outside the generator case 50 by the two independent parts of the rear bracket 52 and the cooling cover 77. As a result, there is a problem in that the section where is responsible for the cooling function by the cooling fluid 90 has a complicated structure.